This tutorial builds on the earlier XUL Template Primer introducing extended XUL template syntax, illustrating the addition of multiple elements. Mozilla then selects from only the data meeting the criteria of the rules to build content.

Now that we've made all of our interface and preferences changes that we can through the browser interface, we can close the browser and start hacking the code. Once you've closed Firebird, browse to the main MozillaFirebird directory and open the subdirectory "chrome". The chrome directory is where Firebird stores all of its JAR files. In these JAR files are packaged all of the XUL, JS, CSS and image files necessary for defining the browser interface, its various elements and how they look and behave. In this tutorial, we will be working exclusively with the browser.jar file.